Criminal behaviour and violence may be the consequence of head injuries acquired during childhood and youth (gang fights, domestic violence, small blows to the head while driving, falls and so forth). In this study, a comparison was made of the school and head injury histories of violent and non-violent prisoners. It was found that the delinquent subjects in both groups had a history of academic difficulties. However, what differentiated the violent from the non-violent group was a history of having suffered head injuries that were never treated. Problems at school are not enough themselves to predict violent behaviour. A history of discrete neurological damage as a consequence to blows received to the head must also be present. The results suggest to the authors that the treatment of the cognitive, behavioural and emotional consequences of brain injury could be a measure for crime prevention. Measures both for prevention and rehabilitation are discussed.